May 28, 2010 -- Women who do weight-lifting exercise routines may be better off drinking two large glasses of milk than sugar-based energy drinks after workout regimens, a new study shows.

McMaster University researchers in Canada report they found that women who drank two large glasses of milk after weight-lifting exercises gained more muscle and lost more fat than women who drank sugar-based energy drinks.

The finding is published in the June issue of Medicine and Science in Sport and Exercise.

"Resistance training is not a typical choice of exercise for women, but the health benefits of resistance training are enormous," says Stuart M. Phillips, PhD, professor of kinesiology at McMaster University in Hamilton, Canada, in a news release. "It boosts strength, bone, muscular and metabolic health in a way that other types of exercise cannot."

A previous study involving men showed that they gained muscle mass and lost fat after exercising and drinking milk.

Phillips says he and his research team aren't sure what causes the result, but more study is being done.

In a three-month period, researchers monitored young women who did not previously perform resistance-training exercises. Two hours before exercising each day, the women weren't allowed to eat and were only allowed to drink water.

But after their routines, one group drank 500 milliliters, or about 17 ounces, of fat-free white milk. The comparison group drank a substance that looked similar, but was actually a sugar-based energy drink. An hour after exercising, the same drinks were drunk.

Exercises included three different types: pushing exercises such as bench presses, pulling-down routines such as triceps push-downs; and leg exercises such as leg presses and hamstring curls.

"We expected the gains in muscle mass to be greater, but the size of the fat loss surprised us," Phillips says in the news release. "We're still not sure what causes this but we're investigating that now. It could be the combination of calcium, high-quality protein, and vitamin D may be the key. And conveniently, all of these nutrients are in milk."

Drinking Milk and Exercise

Phillips says the women who drank milk barely gained any weight, because what they gained in lean muscle balanced out with the loss of fat. Thus, it seems that "simple things like regular weightlifting exercise and milk consumption work to substantially improve women's body composition and health."

The participants were not accepted for the study if they had participated in any resistance training for the eight-month period prior to the study. However, the women were aerobically active. The researchers also excluded women who had consumed any dietary supplements, such as vitamins or minerals, in the previous eight months. Five women in each group were taking oral contraceptives.

All of them were told to maintain their usual dietary patterns. Twice during the 12 weeks the women were summoned to the laboratory for a routine fasting blood sample, all of which were analyzed.

All the young women were of similar height, age, and weight; compliance with the regimen was deemed excellent -- as were the results.

Women drinking milk and exercising lost fat mass, while gaining lean mass and strength. Body mass increased in the control group, however.

Upper-body strength gains were particularly noted. The researchers speculate a reason for greater strength gains may reflect "a greater potential for change in women because of their lower initial upper-body strength."

Vitamin D consumption also appeared to be a factor, according to the researchers. While more research is needed, the researchers write that drinking milk seems to be good for women undergoing resistance-strength training, possibly strengthening their bones.